A power supply circuit using PWM control is conventionally known. The power supply circuit outputs a desired output voltage by controlling, by a PWM signal, ON/OFF of a switching transistor, in which a main current path is connected between an input terminal and an output terminal. The PWM control controls falling of a PWM signal by a comparison between a feedback current and a predetermined control value. Therefore, in the case where an ON time of the PWM signal is short, more specifically in the case where a Duty is small, a circuit configuration for comparing a feedback current and a control value at a high speed becomes necessary. To realize a circuit configuration capable of a high speed circuit operation, generally a circuit consumes a large amount of power. It is necessary to manage to achieve control of a power supply circuit with low power consumption in the case where an ON time of a PWM signal is short.